We performed a constant current stress at forward bias on organic
heterojunction solar cells. We measured current voltage curves in both
dark and light at each stress step to calculate the photocurrent. An
existing model applied to photocurrent experimental data allows the
estimation of several parameters such as generation, recombination,
dissociation rate, and nearly zero field voltage within the active layer
as a function of the stress time. The analysis of extrapolated
parameters shows that the stress mainly affects the recombination rate
of the polaron charge transfer states.